Why are the speakers on the PC phoning?

Question

Audio

In general, at some point (perhaps after moving from one apartment to another), the speakers began to flicker. The speakers are the simplest, defender 2.1 (I don’t remember the model, but they are no more than 3 months old). I thought that they had died, I ordered new ones (also defender 2.1, but a different model), but it was not there. These also phonate from the very moment they are connected to the PC. They do not emit sound only when the sound is turned off in the speakers (the sound on the PC does not play a role). By the way, the speakers are connected via usb, both old and new. I tried both inputs (rear and front), the situation has not changed. But when I connect the headphones to the PC, there is no problem, only the speakers emit sound. I connected the speakers to another laptop (on Windows) - they emit sound. Connected to the poppy - no phonyat. Googled, tried to update the drivers, delved into the sound settings, all in vain.
PS There was a problem with the headphones, I couldn’t hear the voice (Skype calls, a conversation in some game, it was audible, but very quiet even at max volume. I heard all other sounds normally, maybe something was with the frequency of the waves, in general, not I rummage in this) I solved the problem with the headphones by plugging them into another input

Answer 1

1. Poor shielding of the signal cable, or a normal wire is used instead of a shielded wire.
2. Bad contact or breakage of the screen in the signal cable (personally, this was the most common cause for me).
3. Defect in the power supply of the speakers - dry filter capacitors, leakage between the high and low voltage sides, etc.
4. Unsuccessful ground wiring (for example, separate grounds for speakers and computers) or its complete absence.
... and much more.